1. Field of the Invention
The present invention relates to a coating composition for treating colour sensitivity of a colour picture tube, and in particular a composition comprising a silicate, a dye or a conductive material, and dimethylfluoroamide and methyl cellosolve as organic solvents. By dissolving in dimethylfluoroamide and methyl cellosolve, the coating composition according to the present invention can not only delay gelation time of the composition, thereby improving storage, handling and spread properties of the composition, but also forms a coated film having a very uniform thickness and high strength.
2. Description of the Related Arts
A colour picture tube has advantages in that the tube is not limited in colour which exhibits an image, can be easily produced with low cost, and has high resolution. Accordingly, it is a very important display device to be widely used for televisions, monitors for computers, X-rays, measuring machines and the like. The colour picture tube consists of a panel having a fluorescent film of red, blue and green on the inner surface thereof and a bulb provided therein with an electron gun. The colour picture tube can exhibit an image by luminating a fluorescent material as an electron beam emitted from the electron gun is radiated to the fluorescent film of the panel. Accordingly, the colour picture tube is a so-called active type display which can exhibit an image by self-lumination, and an image thereof is very bright. The bright image is not critical in a television, however, there are undesirable effects when an operator continuously watches a screen, such as a monitor for a computer, from a short distance for a long time. Furthermore, fluorescent material which is luminated when exposed to an electronic ray, when the colour picture tube is in operation, cause a great deal of static electricity to be generated on the display and dust particles in the air easily adhere to the display due to the static electricity. In order to solve this disadvantage, various compositions for improving colour sensitivity and preventing electrification of the colour picture tube have been developed and the outer surface of a panel exhibiting an image has been coated with the composition. At the present time, a composition which is prepared by dissolving a silicate, a dye, a conductive material and the like in a mixed solvent comprising methanol and isopropyl alcohol has been generally used as a coating material for treating colour sensitivity of a picture tube. However, the composition has poor flow property and stains in a comb pattern on the surface of the picture tube after coating. Further, formation of occurs too early and it is difficult to preserve the composition. Also, the film is frequently scratched because the film strength is low.